I believed it in that manner always, for the different sound of different sound transmission chains mostly the different frequency procession the responsible.
I hope for it, can be solved, what I wanted to express.
Gyuri
The eternal survivor, but for what?
I hope for it, can be solved, what I wanted to express.
Gyuri
The eternal survivor, but for what?
okapi said:
In principle I would agree, but one valid concern is that such a distortion measurement should be done under circumstances that are (very) close to music reproduction. A single freq measurement is not that. That is why I mentioned the ISO31 multitone which exercises the amp with a rich spectrum of 31 log spaced full level tones between 15 Hz and 20 kHz, which might even stress the amp more than music.
okapi said:
Nfb is everywhere in ourselves and the physical universe. We would not live another minute without nfb, our hearts would stop, we would have to try to breath conciously (and even that needs nfb), we could no longer walk or drive or lift something to our mouths. In other words, without nfb life would be somewhat awkward. 😉
Jan Didden
GRollins
It could be just freq resp. Speakers on their own, if bright in the mids, are often described as "forward sounding".
It could be just freq resp. Speakers on their own, if bright in the mids, are often described as "forward sounding".
janneman said:
I suspect Carver used similar techniques in the infamous "my amp sounds like your amp" incident. Null bridge techniques are one of the greatest innovations of 19th century science/engineering.
janneman said:
If I knew why the Hafler test was a failure, I might be able to suggest a solution. At one point I saw a list of amps that the Haflers beat using their cancellation test. It's been over twenty years and I don't remember what was on the list, but I seem to recall that there were quite a few circuits that would qualify as high feedback. Levinson, I think, had several entries, and they're not shy about feedback. So does Hafler use less feedback or more than Levinson? Is feedback the only factor involved in the cancellation test? Do the amps in question actually sound good?
Most people I know regard '80s vintage Haflers as decent, but not world-beaters. I own a small herd of DH-200s that I use in my AV system and as guinea pigs for Evil Experiments. I sold Hafler in the '80s and compared them head to head with quite a few other amps (their preamps were terrible...non-starters in any race under any conditions, period), both tube and solid state. They were very good for the money and pretty good in the context of the era, regardless of price, but certainly not upper echelon. Trust me, had I thought the Haflers were top o' the heap, I could have saved scads of money. Considering that I was living hand to mouth at the time, I would have had no problem getting something less expensive.
In passing, I might note that negative feedback is not an unmitigated blessing, even--perhaps particularly--in the human body. Consider the auto-immune diseases, for example. Some are damned uncomfortable...some are fatal. This tends to weigh against the "nature uses negative feedback, so it must be good" viewpoint.
fredex said:
Same speakers. Same music. Same everything...just changed the amps.
Grey
GRollins said:
There were two main reasons why the Hafler test fell out of grace:
Too difficult technically (need to twiddle drifting pots and cap trimmers was too hard to make it an easy, routine test);
The audio community simply couldn't stomach the results.
It didn't really fail as such.
Jan Didden
janneman said:
thanks for your helpful reply - i get it now.
janneman said:
i completely agree. i also take these measurement from the amp terminals while the amp is driving a speaker attached with a realistic length of cable.
i also find it informative to play the difference wave back and see what i can hear.
Nelson Pass said:
Nelson, is there another element that common measurements overlook? Are you hinting at it when you write: "If you want the peak distortion of the circuit of figure 13 to remain below .1% with a complex signal, then you need to reduce it by a factor of about 3000. 70 dB of feedback would do it, but that does seems like a lot.
By contrast, it appears that if you can make a single stage operate at .01% 2nd harmonic with a single tone without feedback, you could also achieve the .1% peak in the complex IM test.
I like to think the latter would sound better."
GRollins said:
This example only tells me that negative feedback used incorrectly can cause problems. It does not argue against the original purpose of the analogy, which is to say that because feedback is so ubiquitous that it must be an efficient/advantageous way of doing things. Also, the immune system is a poor/loose example of negative feedback loop. Feedback inhibition is a much more analogous to electrical circuits, and when this goes wrong (too little feedback) it can lead to epileptic seizures as a result of unabated feedforward excitation.
okapi said:
No. My point is that real circumstances conspire to make distortions
higher in peak order and magnitude than you might think.
With complex material and nonlinearities you can get some serious
distortion transients, and you want to consider their audibility.
I am informed that the brain is sensitive to correlated components and
uses them to distinguish and group sounds. IM distortion creates
mixed correlations with sounds modulating other sounds, and you can
check it out yourself with a low quality single-ended tube (or a Zen 🙂 )
playing a complex orchestral piece at a realistic level.
😎
GRollins said:
Less NFB in the tube amp => less damping => bass bloom (very slight) => recessed image.
GRollins said:
They were not. They were quickly replaced by units with auto-nulling and auto-tuning.
Something like that happened recently to the Hafler test with the introduction of Audio Diffmaker by Bill Waszlo.
Still leaves the problem of the mental or intellectual acceptance of course.
Jan Didden
GRollins said:
And what about mysterious interaction between source impedance and load impedance? Did you check the frequency response?
How come you assume that you're the only one aware of this fact?
Would you mind clarifying what you mean by this? Do you prefer a high noise floor of your system?
But that's not the way it is.
Why not measure phase response instead of assuming things regarding it?
/Peter
GRollins said:
And that would likely change the freq response.
I wouldn't conclude there was something mysterious going on until I had exhausted all the known and measurable things.
GRollins said:
Why assume the deepest null (more electrically accurate) amp has a listening preference? I think more that nothing (detectible with even the best imstrumentation) happened when popular tweeks were applied. The null can be done at the speaker terminals BTW. Or the other side of this is that simple frequency response deviations jump out after nulling say for instance two different cables.
scott wurcer said:
Good question. The answer is often, "well if measurements actually meant something, then I should prefer an amp with lower distortion but I don't". The assumption being that they are hearing or not hearing something that at present doesn't show up in measurements.
It is more probable that they just don't like the sound of their source without some added sauce. 🙂
fredex said:
That would be what John Horgan would call the "mysterian" position,
which is the audiophile version of vitalism or the "ghost in the machine".
I don't adhere to the mysterian position, but I do believe that the brain
is remarkably good at teasing information out of sound.
😎